Joins 'Celebrity Big Brother' Cast

Lamar Odom is going back to TV -- the former Lakers star will be joining the cast of "Celebrity Big Brother" this season ... where he'll be competing for a $250,000 cash prize.

The series announced Odom will be a guest for its third season on Thursday ... releasing a video on social media introducing all the celebs who'll be living under the same roof for the competition.

"My name is Lamar Odom [and] people may know me for winning two championships with the LA Lakers," Odom said in his intro.

"They also may know me for marrying Khloe Kardashian. We had our own TV show. Our own reality show."

Odom is no stranger to television -- when he was still married to Khloe, they had their own show, "Khloe…